Telephone system



Nov. 29, 1932. J. E. OSTLINE Ei' AL- TELEPHONE SYSTEM Filed April 14, 1930 13 Sheets-Sheet 1 Nov. 29,1932. v .1. E. OSTLINE ET AL 1,889,564

TELEPHONE SYSTEM Filed April 14, 1950 13 Sheets-Sheet 2 l l I 2 dl '/k fr? 1 Charles Edmund Baal:

Nov. 29, 1932. I "J. E. OSTLINE ETAL 1,839,564

- TELEPHONE SYSLTEM Filed April 14, 1930 13 Sheets-Sheet 3 John Ellis minim:

Reginald Elm" Charles Edmund Beale Sml o T 5 GS K58 PSI 0 #4 s1 v I SM Inu'enfur':

1932. .1. E. OSTLINE ET AL 1,339,564

TELEPHONE SYSTEM Filed April 14, 193C 13 Sheets-Sheet 4 IIar Jul-m EE: 5511111:

Nov. 29, 1932.- J. E. OSTLINE ET AL TELEPHONE SYSTEM Filed pril 14, 193e, 1s Sheets-Sheet 5 Nov. 29, 1932. J. E. OSTLINE ET AL 1,389,554

TELEPHONE SYSTEM Filed April 14, 1950 13 Sheets-Sheet 6 John Ellis U's'flinE Reginald Tgglnr m Beale Charles Ed un Nov. 29, 1932. J. E. OSTLINE ET AL 1,889,564

TELEPHONE SYSTEM Filed Aprii 14. 1950 13 Sheets-Sheet 7 is; v a

Inventors John Ellis Gflina Reginald @1131" Charles Edmund Beale Hit Nov. 29, 1932. J. E. OSTLINE ET AL 1,889,564

TELEPHONE SYSTEM Filed April 14,1950 1s Sheets-Sheet s Charles Edmund Beale 1932. J. E. OSTLINE ET AL 1,839,564

TELEPHONE SYSTEM Filed April 14, 1950 13 Sheets-Sheet 9 Jnl'ln Ellis D's nine Reginald Tylun Charles Edmund Beale Nov 25); 1932. J. E. OSTLINE ET AL 1,889,554

TELEPHONE SYSTEM Filed April 14, 193C 13 Sheets-Sheet 10 s! 13H CS lg N .IIHYY 55L- ZK I dip-KE NOV. 29, 1932. os ET AL 1,889,564

I TELEPHONE SYSTEM Filed April 14, 195C 15 Sheets-Sheet ll 1% V l ks9 in H l l M \AIW.

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' H45 1 1'? Fly 11 l l Inuan DPS Jul-m EH15 [Jinn-1E Hegmald @112? Charles Edmund Beaks 1932- J. E. OSTLANE ET AL 1,839,564

TELEPHONE SYSTEM Filed April 14, 1952 15 Sheets-Sheet 12 B l o n i o o a o a n Inuit-Liars Jul-Ln EH15 U'ETHinE Reginald T MP Charles Edmund Beale Nov. 29, 1932. J. E. OSTLINEQ ET AL 1,839,564

TELEPHONE SYSTEM Filed April '14, 1930 13 Sheets-Sheet l3 KT T 1 RS V Q h -|:1 KTS JRF 5 John Ellis UETline Heqinald Elm" Charles Edmund Beale Patented Nov. 29, 1932 U E AT T NT omcis onNELLIso'srnIiaE; or. CHICAGO, rumors; REGINALD TAYLOR, or nrvnnroon, arm

' crmnnns EDMUND BEALE, or LONDON,

PHONE- AND TELEGRAPH coirrnmr, or, cmoaoo, ILLINOIS, A'CORPORATIQN'OII" DELAWARE ENGLAND, ASSIGNORS r0 ASSOCIATED TELE- TELEPHONE 'sYs'rnM A pplicati onifiled April 14; 1930, Serial .No. 444,022, and in Great Britain May 1, 1829. l

The present invention relates to telephone systems and is more particularly concerned wlth systems including both manual and automatic exchanges 1n which case 1t -1s necessary to provide special equipment for setting up calls fronimanual to automatic exchanges and vice versa; The invention is concerned only with the setting up of calls from a manual exchange to an automaticfexchange and relates to specialtrunking arrangements whereby this. may be done directfroman' A operators position, without the necessity for handling by a B operator located in the automatic or some intermediate exchange.

The simplest method ofzoperation is to providethe A operator with a dial which can be connected with any cord circuit at her position and by means of which she-transmits impulses over the trunk-tobe used for the connection which. sheherself selects by means of the usual tests. This arrangement, however, may be objectionable. in :certain cases owing to the necessity for someconsiderable changes in the standard cordcir'cuits used for pure manual calls and moreover the use of a dial is somewhat laborious and-rather slow. Accordingly arrangements have ,already been proposed'whereby the operator is provided with a keyset which however gen-.

erally necessitated either the provision of a considerable .amount of equipment 1n the manual exchange, which is undesirable, or

the transmission of special-pulses involving the use of marginal or, polarized relays. It

has also been proposed that the particular trunk which was to be used for a calls'hould be selected by an automatic switch and indicated to the operatorona lamp panel or the like i The object .ofthe presentinvention is to provide an improved arrangement whereby the operator ,herselflsele'cts the junction which will be used so that'no lamp panel orsimilar additional equipment isnecessary at her position while the determination of the impulses to be transmitted is effected from a key-set over a four conductor-keying trunk.

According to onefeature. of the invention in a system-including both manual and automatic exchanges and having calls from a means of a key-set, the momentary operation of aokey is adapted to efliectthe association of the key-set with a common control line to an automatic exchange, the association be manual exchange set up by an operator by ing maintained until the; fullwnumber has been registered at the automatic exchange or a release key is operated.

Accordingjto another feature of the invention a line extending to an automatic ex change and common to a plurality of operaed at the incoming end with a common control line extendingto that exchange. I

The. invention will be better understood from the following description of several methods of carrying it into effect which should ,be taken in conjunction with the accompanying drawings. It will be understood, however, that-the invention is not limited to the specific embodiments shown and that various alterations to the circuit details such as mayreadily-be carried outby those skilled in the art would come withinits scope.

. Referring now to the drawingspFigs. 17

show detailed circuits of this arrangement.

Of these drawings, Fig. 1 shows the .keys at the operators position and the jack terminating one junctiontogether with thetrunk finder switch for associatin the operators key-set with the keying trun corresponding to the order wire key depressed. Fig. 2 I

shows the trunk relay set at the incoming end of the junction, together with the junction finder switch for associating the keying trunk with the junction. Fig. 3 shows the sender finder for associating a free register sender with the junction. Figs. 4:, 5, 6 and 7 show the detailed circuits of a suitable sender.

In the arrangement illustratedin Figs. 1-7 the method of operation is that the operator keeps the order wire key depressed until she secures control of the order wire as indicated by the lighting of the guard lamp associated therewith and then tests in themultiple for a free junction. This arrangement is open to the objection that the order wire is being held during the time that the operator is making her test for a free junction and this time will probably be comparable with and may even exceed the actual time taken to key up the number. Accordingly, Figs. 8 and 9 show a modification whereby the operator first plugs into a free junction and then presses the order wire key so that as soon as she obtains control of the order wire she may key up the number and thus more economical use is made of the order wire.

Figs. 10-12 show a further modification in which the junction finder switch at the automatic exchange has been eliminated, the order wire being associated with the required junction by means of a switching relay,the circuits being such that it is impossible for the order wire to be associated with two junctions at the same time. Fig. 13 shows diagrammatically the general layout of the system illustrated in Figs. 1-7.

The operation of this system may first be traced through briefly with reference to Fig. 13. Assume that an operator at position 1 having ascertained the requirements of a calling party wishes to set up a connection to the automatic exchange shown, she will depress the order wire key 01 momentarily, whereupon the associated keying trunk finder TF1 will start hunting under the control of the position relay set PBS to associate its wipers with the keying trunk KT extending to the required exchange and when this has been done, guard lamp L1 will commence to flicker. In the meantime the operator will test in the usual way for a tree trunk outgoing in the required direction and having found one will plug into the corresponding jack J1. Thereupon circuits completed over the trunk T for relays in the trunk relay set TRS will cause the sender finder SF associated therewith to select a free sender S and at the same time the first selector E will be prepared for operation. Meanwhile or as soon as a free sender has been associated with the trunk relay set, the finder RF associated with the keying trunk relay set KTS will operate to connect the keying trunk with the trunk relay set TRS. This operation of course will only take place assuming that the keying trunk KT is not already in use and if it should happen that another operator is using the keying trunk at this time, the op- F' a a o erator under consideration Wlll have to Walt until it becomes free. When the operator obtains connection with the keying trunk, that is to say, when the switch RF finds the trunk relay set TRS, the operator will ieceive two short tone signals and she will then commence to operate the keyset K1 for the four digits of the wanted number. This effects the connection of suitable potential to the four leads of the keying trunk in various combinations and since these leads are now extended through to the sender, it will now send out the appropriate trains of impulses for operating the selector E and suitable succeeding switches. Conveniently the sender commences sending as soon as the first digit has been registered since this reduces the holding time of the senders and hence enables the number required to be kept as small as possible. The keyset is disconnected from the keying trunk and the guard lamp is extin- 1 guished as soon as the call has been completely set up. Supervision of the call is ofiected as on manual-to-manual calls.

In case the operator should realize that she has made an error in setting up the number, she will cancel by withdrawing the plug from the trunk jack, depressing the order wire key again momentarily and replacing the plug, in consequence of which the operated apparatus is released and the setting up of the call may take place correctly in the manner previously described. This arrangement readily permits cancellation to take place at any stage of the setting-up operation without introducing a large amount of complicated equipment.

It may be mentioned that if the manual exchange had access to only four or less automatic exchanges, it would probably be preterable to employ relay switches in places of. the rotary type keying trunk finders shown.

Considering now the detailed operation of the circuits shown in Figs. 17, it will be assumed that the operator on receiving a call plugs into the answering jack of the calling subscriber with the answering plug of a cord circuit of known type and ascertains that he requires connection to a subscriber attached to a particular automatic exchange. She will thereupon depress the order wire key associated with this exchange which will be assumed to be that shown in Fig. 1 and designated O1, whereupon a circuit will be completed from earth over the lower springs of the key, high resistance right-hand winding of relay KT, armature 70251, interrupter springs tml, very high resistance winding of relay GT to battery. Relay GT alone operates in this circuit and at armature gt1 completes a circuit for the driving magnet TM of the trunk finder switch TF, whereupon the magnet operates and at the interrupter contacts tml opens the circuit of relay GT. Furthermore at the upper springs of the key ()1 battery through the winding of relay TS is extended over armature trl to the associated contact in the bank of wiper The interaction between relay GT and driving magnet TM'advances the wipers of the trunk finder switch TF until they encounter the marked bank contact whereupon relay GT will be shunted out in a circuit including the low resistance left-hand. winding of relay KT, the wiper and bank P and winding of relay TS to battery. Since-relay GT cannot again operate, the switch is brought to rest and relays KT and TS are Operated inseries, the former at armature'ktl completing a holding and guarding circuit byvway of its low'resistance left-hand winding to earth at the release key R. In order that there shall be no possibility of one operator being connected with a keying trunk which has been marked by another operator, the P banks of the trunk finder switches TF at the various positions are not commoned together, so that the depression r of an order Wire key similarto 01 onany position only results in the marking of the appropriatebank contact of the trunk finder switch associated with that" tacts of the other switches, thereby busying this particular trunk to all the operators. Thisoperation also completes a lockingcircuit for relays TS and KT so that-the order wire key may now be released. The operation of relay KT moreover at armatures 7M2 70255 connects up the keyset numbered 1 to by way of the wipers of the trunk finder switch TF to the selected keying trunk in readiness for the required number to be set up by the operator, whileat armature 7ct6 in? terrupted earth ofconveniently 2 secs. on and 2 secs. off is connected to the position guard lamp FL, thereby indicating to the operator that she may now release the order'wire key 01 and proceed to test in the usual manner for a free junction leading to the required exchange. In order to simplify and shorten the process of testing for an idle junction it may be desirable in some cases to employ known group testing arrangements for instance those'employing chain contacts on the sleeve'relays such as S by'means of which a special relay may be operated when the chain is complete to eflfect the connection of discriminating tone to a master ack t-OlIlCllCEltB' that allthe lines of the group are-busy,

In case all the junctions should happen to be busy at this time, the operator will be unable to-set up the connection and will'momentarily press the release key R to free the keying trunk. T hereupon relays KT andTS are de-energized and the connection of the operators keyset to the keying trunk is broken so that she may proceed withthe setting up .ofanother call and moreover the keying that shown, she will plug in to the associated jack thereby extending battery from the cord c1rcuit over the ring conductor 11 to operate relay L in the junction relay set JR, Fig.- 2.

Relay L on energizing prepares the associated group'selector for operation by completing a loop from negative conductor,.resting contacts of armature 70.91, armature'll, winding of hi h impedance relay I, left -hand winding of shunt field relay D, resting contacts of armature 7082 to the positive conductor. Furthermore at armature 7:2 relay B is operated,

thereupon at armature 61 extending earth 1 over armature 'frl and resting contacts of armature 70701 to operate relay SJ of the keying trunk relay set. Relay SJ in operating, at

armature sjl which closes first, connects up the low resistance upper winding of relay to wiper S1 and at armature sj2 connects up the high resistance lower winding of relay KK. Consequently it the wiper S1 of the junction finderRF is resting on a contact other than that marked with battery by'the operation of armature 722, Fig. 3, a circuit will be completed from earth, armature 62 of a relay set not in use, bank contact and wiper S1, armature sjl, upper low resistance winding of relay KK, armature 70702, interrupter springs rml, high resistance winding-of relay GJ to battery. A branch of this circuit extends to earth. through the lower winding of relayKK butalthough relay GJ is operable in thecircuits traced, its extremely high resistance prevents the operation of relay KK at this time. Relay GJ on operating its armature gjl completes the circuit of the driving magnet RM'of the finder switch RF, and as a result of interaction between this magnet and relay GJ the wipers of the switch are advanced until wiper S1 engages the marked contact in which position the keying trunk is associated with the selected junction relay'set.

When the wipers reach this position relay GJ will be shunted out by battery through. the low'resistance' winding of relay PS and relay KK will be operated over the circuit; earth, armature .972, two windings of relay KK in series, armature sjl, wiper S1 and bank contact, armature b2, armature f73. winding of relay PSto battery. Relays PS and KK operate in series in this circuit and at armature 70702 a guarding and holding circuit is completed by way of the low resistance upper winding of KK, at armature 7c7c1 the slow releasing relay SC is operated in series with relay SJ and at armatures 7ck3r7c7t6 the keying trunk is extended to the "associated wipers of the switch RF.

The operation of relay B in the junction CFI relay set also at armature b3 started the sender finder switch SF hunting to find a free sender by connecting wiper P1 over armature 53, upper low resistance winding of re lay KS, armatures 70.98 and 774, interrupter springs sml, high resistance winding of relay GS to battery. It the sender with which the wipers are then associated is busy, earth will be connected to the corresponding P1 contact through the low resistance upper winding of the KS relay of the junction relay set with which the sender is then connected. Relay KS does not operate in this circuit but relay GS at armature 9'31 completes a circuit for the drivin magnet SM of the sender finder switch SF which energizes and brings down relay GS by opening interrupter contacts sml. Relay GS and magnet SM interact in known manner until wiper P1 of the switch encounters low resistance battery by way of relay BG, Fig. 5, in a free sender, for instance that shown. Relay GS is then shunted out and the rotation of the sender finder switch is stopped, but relay KS is run able to operate to seize the sender until armature p31 is operated when the junction relay set has been found. Thereupon a circuit is completed from earth, armature ps1, both windings of relay KS in series, armature Z28, wiper P1 and bank contact, conductor 12, armatures 001 and M31, Fig. 5, winding relay BG to battery. Relays BG and KS are operated in this circuitand the latter relay at armature 7088 completes a holding and guarding circuit by way of its low resistance upper winding. Moreover, at armatures ksl and 7082 the operating circuit of the group selector is transferred to the sender circuit, at armature 7383 a circuit is prepared for relay FR, and at armatures Face-Jae? the keying trunk is extended over the wipers of the sender finder switch SF to the seized sender. Relay BG in addition to performing other circuit changes, at armature 69S completes a circuit from earth, armature s51, lead 17, armature 693, resting contacts of armature M2, armature cs3, winding of relay TA to battery. Relay TA is slightly slow to pull up and on operating at armature ms completes a circuit for relay TB which is also slow to pull up. Vhen relay TB energizes, it. completes a circuit for the further slow-to-pullup relay TC at armature T352 and relay T C- then locks up at armature 2502 and brings down relays TA and TB. The operation of relay BG moreover connects up a tone circuit from conductor 13, Fig. 7, condenser arinatures m2 and #01, conductor 14, armature 692, Fig. 5 conductor 15, bank con tact and wiper S2, Fig. 3. armature 7e33, conductor 16, winding of relay FR, right-hand winding of the shunt field relay D to battery. Relay D is provided with a good magnetic circuit and accordingly the tone is induced in the left-hand winding and is thus transmitted over the junction to the operator. The application of tone is made for a period corresponding to the operating time of relay TA,1when it is removed at armature me. After a pause corresponding to the operating time of relay TB it is again applied at armature tbl and is then removed at armature Z01 when relay TC operates. The operator thus receives two short tone signals to indicate that the sender is in condition to register the wanted number.

The operator will now commence operating her keys to set up the required number, which will be assumed to be 4325. Upon the operation of key at, a circuit is completed from earth, operated springs of key 4:, armature lai -i, wiper Y and bank contact of the trunk finder TF, wir ling of relay YR to battery. Relay thereupon operates its armature girl thus ext nding earth over the junction conductor 18, armature 761 175, wiper Y1 and bank contact, conductor 19, armature 7036, wiper Y and haul: contact, conductor 20, wi er DD?) and first bank contact of digit r ibutcr switch DD, left-hand winding 01? =age relay M" winding of common bata 7 feed relay DS to battery. Relays MY and DS operate in and the former at armature inc 1 completes a locking circuit for itself over its right-hand winding and lead ill to earth at armature bye. Relay DS on operating, at armature (Z81 energizes the driving magnet DDM of the distributor switch ED, so that when the operator releases key etnd thus opens the circuit of relay DS, the ibutor switch wipers will be advanced to the second set of bank contacts, thereby connecting up the second group of storage relays Cl' v, CX, CY and CZ. Moreover when the distributor switch DD takes its first step a circuit completed from earth at armature 0gb, Fig. 5, wiper DB2 and second bank contact, resting contacts of armature a? and winding of relay SS to battery, whereupon relay SS operates and locks up over conductor 21 to earth at armature 694. The operation of relay SS again completes the tone circuit over conductor 18, Fig. 7, condenser Q, armatures an and 885 to conductor 14: and thence as previously traced, so is to provide an indication to the operator hat the sender is functioning correctly and that she may proceed to set up the remainder o the digits. After the operating period or relay TA whose circuit is completed at armature the tone circuit is opened at armature m1. Relay SS also opens the homing circuit of the sender switch at armature and at armature cs1 completes a circuit rom earth, armatures 881 and 824i, winding 1? relay CC anl resistance 22 to battery. Relay CC is short-circuited intermittently by the impulse springs 23 which may c0nveniently be operated 10 times per second but when the springs open relay CC operates and relay BP. The Wipers S1 "and S2 ofthe.

sender switch SS are now stepped round their associated banks and as soon as wiper S1 moves off normal, relay is operatedthereupon at armature salremoving the shortcircuit round impulse springs 24 and thus permitting them to become effective :to send impulses over, the outgoing conductors;

Springs 24 are operated at the same speed as springs 23 and consequently for each impulse.

sent out for operating the automaticswitches the sender switch is advanced one step. When four impulses have been transmitted to the group selector, correspondingtothe number keyed,- wiperSQof the sender will engage its sixth bank contact and-a'circuit may thenbe traced from'earthjat wiper C2 and first bank contact of the controlswitch CS, Fig. 7, conductor 25, armatures mw2, mmfl, myZ and 'mz3, lead 4, which is assumed to be connected tolead .4 opposite bank contact 6 and wiper S2 of the sender switch SS, lower winding of relay ,SZ to battery. 1 Relay SZ accordingly operates and at armature s22 completes a lockingcircuit for itself, at arma tures 821, Fig. 4, short-circuits the impulsing springs 24 to prevent the transmissiono'f further impulses at this time, at armature s24: opens the stepping circuit of thesender switch driving magnet SDM, at armatureszf) prepares a circuit for its-upper winding, and at armature s23 completes an automatic homing circuit'for .the sender switch'fromearthby ill) way of bank comlnoning and wiperlSl armature s23, interrupter springs sdml, winding of magnet SDM to battery through the low resistance relay BP. I v

The Wipers of the sender switch are accordingly driven to the next home position, for instance, contact 13, whereat wiper, S1 no longer encounters earth and thus thecircuit of the magnet and relay SA is opened. Upon the release of relay SA after its slowperiod the'circuit of relay SZ is also opened andit releases after a slight interval and at, armature 8245 again completes the circuit foradvancing the sender switch. Moreover upon the release of armature m3 magnet CDM will de-energize and accordingly the wipers of the control switch CS will he stepped into engagement with the second set of bank contacts, in readiness to extend earth from wiper C2 over conductor 26 to the second set of storing relay group armatures, which; arenot shown but are identical. with those of the M group, and'are multiplied tothe sender switch bank in thesame manner.

If due to some slight delay in keying, the second digit should not. be fully'set ,upat this time, the wipers of the distributor switch DD will be standing on the secondsetof Relay nectingrelay TR.

bank contacts and a circuit will be completed from earth atarmature I296, ig. 5, wiper DD2 and second bank contact, conductor 27, secondbank contact and wiper C3'of the control switch, Fig. 7 conductor 28, armature 8'25, upper Winding of relay SZ to battery.

Z is therefore prevented from re: leasing and restarting the sender switch until the second digithas been fully received, that is when the distributor switch DD is stepped on to the third set of contacts; hence it is not possible for the sending operation to outrun the storing operation. i

When all the digits have been stored, the digit distributor DD will beadvanced to fifth position-whereupon earthwill be connected, from armature bg6 over wiper DD2 in fifth position, conductor 15, bankcontact and wiper S2 of-thesender finder SF, armature ks3*, conductor 16, winding of relay FR, right-hand winding of shunt field relay D a to battery, Relay FR-thereupon operates and completes a locking circuit for itself at armature f'r1, at armature f1'2 'preparesthe bu'syfiash'circuit, at arm'ature f1-4, Fig. 3, opens apoint' in t-he'circuit of relay GSand at armature fr?) brings down relays PS and KK. Relay KK on releasing, opens'the circuit of relays SJ and SC, and-since the latterrelay' is slow to release a circuit istmo-. mentarily completed from battery by wayof the resistance 30, Fig.2, armatures 801 and 70106, conductor 31 of the keying trunk, armature 2T1, Fig. 1, winding of relay TR," armature fz rl, conductor 18 of the keyingtrunk,

armature 70705 to earth. RelayTRthereupon operates over the circuit described and at armature .trl brings down relays .KT and TS so that at armatures'kt2-kt5 the keyset is dissociated from'thekeying trunk-whichis then available for use by other operators.

Relay KS associated with the sender-finder must clearly remain operated until send- I ingfout is completed and, its release is normallydependent on the sender. s

It maybe mentioned that the operation of relay TR in a' loop circuitfrom a battery source at the automaticexchange is convenculties arising fromthe fact thatthe battery neot ,up the earth, at

the same time discon- When the sendingoperation has beencom ient as it satisfactorily overcomes any'diflivoltage employed at the aut0maticexchange' connecting earth directlvto those ,leads en-f' ergiz es relays YRand ZR which then 'con- I .pleted, the wipers of the control} switch CS" will advance into the fifth position, whereupon relay CO'will' be operated from the 'ear-thed wiper C2; Relay COjonoperating connects a shortecircuit 'across th'e impulse leads to the automatic switches at armature 002, Fig. 4r, thereby holding the switch train and preventing any further pulses being sent, and moreover at armature 001 opens the circuit of relay BG. On the release of relay BG, armature bga removes earth from the common holding conductor 21, thereby releasing all the storing relays which were operated and also relays BX and SS. On the release of relay SS a homing circuit is completed for the sender switch SS, Fig. 6, while at armatures 1995 and 594 homing circuits are completed for the distributor switch DD, Fig. 5, and the control switch GS, Fig. 7 respectively. As long as current flows through the magnets the battery feed relay BP will be operated and an alternative holding circuit is provided for relay CO over conductor 29, armature b291, armature 7996 to earth. By this means relay CO is held operated until all switches have reached a home position thereby holding open the circuit of relay BG at armature 001 in order to prevent the premature re-seizure of the sender.

When relay KS releases at the completion of the sending operation owing to the opening of its circuit at armature 001 battery through the retard LA, Fig. 2, is disconnected from the lower junction conductor at armature 7689, thereby indicating on the ordinary supervisory lamp in the cord circuit that sending is completed, while at the resting contacts of armatures ksl and K292 the negative and positive leads extending to the automatic train of switches are disconnected from the sender and transferred to a holding circuit which includes the high impedance winding of relay I and the left-hand winding of the shunt field relay D. Supervision of the call is now controlled by means of armature d1, relay I) being operated when the called party answers by the usual reversal of current from the final switch.

In case the wanted party is busy at this time, battery will not be reversed from the automatic switches but instead simplex batterywill be connected intermittently to the speaking leads thereby effecting the intermittent deenergization of relay I which will fiash'the supervisory lamp at the operators position by opening the battery circuit of retard LA. The operator on seeing the lamp flash will inform the calling party that the number he requires is engaged and that he must call again later.

In case the operator realizes that she has made a mistake in setting up the number, she may cancel by withdrawin the plug momentarily thereby releasing relay B and thus relays KS and BG. The keying trunk is not released however and the operator may at once set up the proper number, a different sender being now employed. Since in the partially operated sender, relay CO will not have been energized, relay BX is made slow so as to ensure that the sender shall not be seized before it has completely restored to normal.

Figs. 8 and 9 show the modifications required to the order wire circuit when a slightly different method of operation is employed in which more economical use of the order wire is secured by arranging that the operator tests for a free junction before pressing the order wire key so that the keying trunk is only in use for the actual time that sending is taking place thereover. This represents a considerable economy since the time required. to select a free junction may quite well. be comparable with the time required to send the Wanted number. A di'fiiculty arises, however, in this case owing to the fact that several operators may have selected junctions to a particular automatic exchange and it is i1nportant that if they then operate their order wire keys more or less simultaneously the keying trunk shall then. be associated with the junction selected by the operator whose keyset has been connected thereto. This is effected by the connection of a special potential over one conductor of the junction to make contacts in an additional bank of the junction finder switch.

Consider now the setting up of a connection from the position shown in Fig. 8 over the junction extending to the equipment shown in Fig. 9. The operator on ascertaining that a call is required to this automatic exchange will test for a free junction in the usual way and on finding one will plug in. This opera tion will effect the energization of relay L which at armature Z1 prepares the associated armature first selector for operation and a Z2 energizes relay B. Belay B thereupon armature b1 completes a circuit for the lower winding of relay KK and relay Gil in series. at armature 724: prepares the connection of marking potential to the lowermost bank of the switch RF and at armature 63 sets in operation the sender finder SF to select an idle sender. It will be understood that Figs. 8 and 9 are intended to be associated with Fig. 3, the only difference being that in the modified circumstances the back contact or armature 62 is no longer necessary. Relay operates as before and interacts with magnet RM to effect the hunting operation of the trunk finder RF.

When the operator now presses the order wire key 01 a circuit is completed for the right-hand winding of relay KT and high resistance relay GT in series and relay GT interacts with the magnet DM to effect the hunting operation of the switch TF. Moreover, at the upper springs of the key 01, battery through the winding of relay TS is connected to the associated contact in the test bank of the switch TF so as to bring the switch to rest when this contact is encountered. As in the arrangement described in Fig, 1, relay TS is then operated in series 'sion of sending. I a p 7 Afurther modlfication 1S shown lllfll lgS. -12, this arrangement also being assumed with relay KT and at armature tel short-circuits the key springs while relay KT at armature 7M1 completes a holding and guarding circuit, at armatures k2 J05 connects up the keyset, at armature M6 causes the lamp FL to flicker to indicate to the'operator'that she has obtained possession of the keying trunk and at armature kt? connects battery to the tip conductor connected with herheadset whence it is extended over the'operated contacts of the speaking key, tip of theplug, t1p spring of jack, conductor 82', armatures #2 and 64: to the test contact associated with the trunk in the bank of thes'witch RF; Hence when the wipers reach this contact, ,a circuit is completed for. relay J F which operates and at armature completesa switchlng circult for relay KK in series with relay fPS; :Relay GJ is now shunted outand the switch is'thus brought to rest and relay KK at armature klal. energizes relay-SC in series with relay JF, at armature ]732 completes/a holding and guarding circuit, and atlarmatures M43 3706 sWitchesth-e keying trunk through.

The, operator will now proceed to key up the required number in the usual manner, thereby effecting the operation of the impulse sender as previously described. When all the digits have been registered, earth will be con nected backto effect the operation ofrelay FR which at armaturefrlcompletes a locking circuit for itself, at armature r-:2 disconnects the special marking circuit and prepares a circuit for repeating busy flash and at armature fr3 brings down relay KK. Accordingly a momentary circuitis completed over the two lower conductors of the keying trunk for relay TR which its a'mature #1 brings down relays KT and TS thereby freeingthe keying ,trunk. hen the full number has been sent out, relay KS is dc-energized and the connection is switched through at arm tures'lcsl and 7052, while at armature ksQ-the operator is givena signal to indicate conclu-v to work in conjunction with the sender. shown inFigs. 1-7..v The operating procedure in this case is similar to that just described, that is to say the operator first selects afree unctron and then operates the order wire key.

In this arrangement, however, the circuits have been somewhat simplified and the nccessity for the junction finder has been eli1ninated, the necessary connections being made directly by relay KK. "The momentary marking potential overf the selected junction however makesit impossible for the keying trunk to become ltSSOClELtEtlWltll more than one junction at a time. This arrangement,

j moreover, removes a possibleobjection to the arrangement shown in Figs; 8 and9 tl' atthe unction finder, RF commences to rotate, as soon as the plug 1S"111S6Il19d.111 the unct1on Referring now to Fig. 10, the procedure is the same as before, viz. that the operator on receiving a request to complete a call to a particular. exchange will test with the tip of the plug in the usual manner for a free junction and on finding one will plug in'thereon. The arrangement of F1 10 shows thegroup busy tone connected directly to the sleeve of the-jack illustrated over chain contacts of the sleeve relays. The operation ofplugging in completes a circuit for relay L at the automatic exchange which at armature Z1 prepares the first selector for operation and at armature Z2 prepares a circuit for relay. B.

When theoperator presses the order vwire key,

atthe lower springs of the key a circuit is completed for relay ST which at armature stl initiates the hunting operation of the switch TF and at armature s62 prepares the connection of discriminating battery over the junction. The upper springs of the order wire key serve as in the arrangements previously described to mark the appropriate contact in the test bankof the switch TF. lVhen the required keying trunk is found, relay KT operates and in addition to performing its usual functions, at armature kt? opens the circuit of relay ST and connects battery over armature 8Z2 and the contactsof the speaking keyto thetip of the plug. This battery connection, which is only applied a's'long as relay ST holds up, serves to energize relayB wh1c h thereupon at armature Z91 locks up dependent upon armature Z2. RelayB also at armature b3 initiates the hunting of the sender finder SF and at armature b2 com-'1 pletes a circuit for relays PS-and KK in series; Relay PS thereupon at armature ps1 completes a switching circuit for relay KS so as to connect up the seized sender and open ,the initial circuit of relay B, while relay KK at armature ik2-lc7a5connects the keying trunkthrough and at armature Mel energizes erelay SC.

The operator will now receive the two short periods of tone and will thereupon operate herlreys in the usual manner. WVhen all the di its hjave been'regi'stered', earth will be connectedup from the sender to operate relay FR -which at armature frl locks' up dependent upon relay B, atarmature frQ disconnects the initial energizingcircuitof relay B and pre pares a c1rcu1tfor repeating busy flash, at

armature fr'dopens a pointin the circuit of relay GS'and at armatures fr4cf'r7 opens the conductors of thekeying trunk so .as to pre 

